Ambon is great at that period, as well as Raja Ampat.
Mid Feb is a little early for North Sulawesi, I've stayed once in Lembeh in Feb and would rather postpone by a few weeks, since it was raining almost everyday, they had to cancel Bangka trips because of the Habagat winds. You'd be better off starting from March usually or stay on Bangka.
It's a pity because Bangka is world class for both macro and wide angle, you should stay ther at least 1 week. Sahaung is probably my favorite divespot worldwide, and like said above, i've never seen that many Pontohi and Severnsi seahorses anywhere.
If you're staying a month, you could consider coupling Ambon for 2 weeks, Raja Ampat for 1 week and N/Sulawesi (Bangka or Lembeh) 1 week. it's also a convenient and easy flight routing coming from Jakarta.